The effective removal of Sb(V) by bio-electrochemical systems: Performance and mechanism

Recently, Antimony (Sb) pollution in wastewater is a global environmental issue. The bio-electrochemical system (BES) converts Sb(V) to less toxic Sb(III) via microbial electrochemical processes. In this study, the effect factors of Sb(V) removal by BES are explored and the removal mechanism by BES is clarified. Results show that under acidic conditions, the removal rate of Sb(V) was 100 %, which is far more than its removal efficiency under a neutral condition. Sulfide concentration critically regulates efficiency: levels >8.5 mg L −1 inhibit removal, while <6 mg L −1 promote it via H₂SbS₄ − formation, linked to sulfate-reducing bacteria (SRB) metabolizing S 2− . Furthermore, the mechanism of bio-electrochemical system (BES) reactor was further clarified by 16 s rRNA high-throughput sequencing. There are three types of bacteria play an important role in the removal of Sb from BES. ARB can reduce directly Sb(V) to sediment (i.e. Sb 2 O 3 , Sb(OH) 3 ) in BES, respectively. Electrochemically active bacteria (EAB) can transfer electrons to Sb(V) in solution by graphite electrodes and promote the reduction in BES. And SRB can use organic matter as electron donor to reduce SO 4 2− to S 2− in respiratory metabolism process. Electric fields can stimulate parts of microbial activities, so that it can improve the removal efficiency of Sb(V). Sb of the wastewater are removed by antimony-reducing bacteria, sulfide reduction, and electrochemistry combined with microbial reduction. Therefore, BES have a good performance in the removal of Sb(V) in acidic wastewater. This study presents a novel method for treating Sb(V), which is more sustainable compared to traditional chemical approaches.